Orphenadrine

Anticholinergic·Musculoskeletal & Rheumatology

Symptomatic relief of acute, painful musculoskeletal conditions (e.g., acute torticollis, severe acute back spasm)

ANTICHOLINERGICNorflex100 mg tabletS4TGA

Max Dose

200 mg/day

Half-life

14 h

Abuse Risk

EUPHORIA

Anticholinergic

SEVERE

Rapid Summary

Overview

Centrally acting skeletal muscle relaxant with potent anticholinergic and antihistaminic properties. Used for acute, painful musculoskeletal spasms (e.g., lower back pain).

Maximum Dose

Max 200 mg/day (Usually 100 mg BD).

Clinical Focus

Highly euphoric with significant abuse potential. Causes severe anticholinergic toxicity (delirium, retention) in the elderly.

Bottom Line

Orphenadrine is an anticholinergic muscle relaxant for acute musculoskeletal spasm, but has high anticholinergic burden making it dangerous in elderly and is cardiotoxic in overdose.

Formulation & Access

Brand Names

Norflex

Oral Routes

Do not crush

Tablets (100 mg - slow release). Do not crush.

Prescribing & PBS

Private script or hospital supply. Restricted due to abuse potential.

Indications & Use

Primary

TGA

Symptomatic relief of acute, painful musculoskeletal conditions (e.g., acute torticollis, severe acute back spasm).

Off-Label

OFF

Drug-induced parkinsonism/EPS.

Clinical Place

Short-term adjunct therapy. Not for chronic use or spinal cord spasticity (use Baclofen instead).

Quick reference

Class & Role

Anticholinergic — Centrally acting skeletal muscle relaxant with potent anticholinergic and antihistaminic properties.

Route / Formulation

Tablets (100 mg - slow release). Do not crush. (Norflex)

Usual Dose & Max

PO 100 mg BD (morning and evening). Max 200 mg/day (Usually 100 mg BD).

Key Indication Doses

Acute Muscle Spasm / Back Pain: PO 100 mg BD (morning and evening). Elderly / Frail: Avoid completely if possible, or start at 50 mg/day. High risk of falls and confusion.

Best Uses

Orphenadrine is an anticholinergic muscle relaxant for acute musculoskeletal spasm, but has high anticholinergic burden making it dangerous in elderly and is cardiotoxic in overdose.

Avoid / Cautions

Glaucoma, myasthenia gravis, mechanical GI obstruction, severe BPH with retention, tachyarrhythmias. Pregnancy Category B2.

Key Risks

Neurological: Euphoria, hallucinations, agitation, severe anticholinergic delirium. HIGH — Dizziness, blurred vision. Cardiovascular: Tachycardia, palpitations, mild hypotension. Gastrointestinal: Severe dry mouth, constipation. Genitourinary: Urinary retention (precipitates acute retention in men with BPH).

Key Interactions

Additive and severe anticholinergic toxicity when combined with TCAs (Amitriptyline), Antipsychotics, and Promethazine. Additive CNS depression with Opioids and Benzos.

Monitoring

Assess bladder output and bowel opening. Monitor HR (tachycardia is a classic sign of toxicity). No specific routine laboratory tests required.

Clinical Pearl

Because of its central NMDA/anticholinergic action, Orphenadrine produces a mild euphoria. Drug-seekers will frequently present to ED faking severe back spasms specifically requesting 'Norflex'. Be highly vigilant and restrict scripts to 3-5 days.

Access

Norflex100 mg tablet

Brand: Norflex
Formulation: Tablets (100 mg - slow release)

Orphenadrine

Anticholinergic·Musculoskeletal & Rheumatology

Symptomatic relief of acute, painful musculoskeletal conditions (e.g., acute torticollis, severe acute back spasm)

ANTICHOLINERGICNorflex100 mg tabletS4TGA

Max Dose

200 mg/day

Half-life

14 h

Abuse Risk

EUPHORIA

Anticholinergic

SEVERE

Rapid Summary

Overview

Centrally acting skeletal muscle relaxant with potent anticholinergic and antihistaminic properties. Used for acute, painful musculoskeletal spasms (e.g., lower back pain).

Maximum Dose

Max 200 mg/day (Usually 100 mg BD).

Clinical Focus

Highly euphoric with significant abuse potential. Causes severe anticholinergic toxicity (delirium, retention) in the elderly.

Bottom Line

Orphenadrine is an anticholinergic muscle relaxant for acute musculoskeletal spasm, but has high anticholinergic burden making it dangerous in elderly and is cardiotoxic in overdose.

Formulation & Access

Brand Names

Norflex

Oral Routes

Do not crush

Tablets (100 mg - slow release). Do not crush.

Prescribing & PBS

Private script or hospital supply. Restricted due to abuse potential.

Indications & Use

Primary

TGA

Symptomatic relief of acute, painful musculoskeletal conditions (e.g., acute torticollis, severe acute back spasm).

Off-Label

OFF

Drug-induced parkinsonism/EPS.

Clinical Place

Short-term adjunct therapy. Not for chronic use or spinal cord spasticity (use Baclofen instead).

Quick reference

Class & Role

Anticholinergic — Centrally acting skeletal muscle relaxant with potent anticholinergic and antihistaminic properties.

Route / Formulation

Tablets (100 mg - slow release). Do not crush. (Norflex)

Usual Dose & Max

PO 100 mg BD (morning and evening). Max 200 mg/day (Usually 100 mg BD).

Key Indication Doses

Acute Muscle Spasm / Back Pain: PO 100 mg BD (morning and evening). Elderly / Frail: Avoid completely if possible, or start at 50 mg/day. High risk of falls and confusion.

Best Uses

Orphenadrine is an anticholinergic muscle relaxant for acute musculoskeletal spasm, but has high anticholinergic burden making it dangerous in elderly and is cardiotoxic in overdose.

Avoid / Cautions

Glaucoma, myasthenia gravis, mechanical GI obstruction, severe BPH with retention, tachyarrhythmias. Pregnancy Category B2.

Key Risks

Key Interactions

Additive and severe anticholinergic toxicity when combined with TCAs (Amitriptyline), Antipsychotics, and Promethazine. Additive CNS depression with Opioids and Benzos.

Monitoring

Assess bladder output and bowel opening. Monitor HR (tachycardia is a classic sign of toxicity). No specific routine laboratory tests required.

Clinical Pearl

Access

Norflex100 mg tablet

Brand: Norflex
Formulation: Tablets (100 mg - slow release)